1. Field of the Invention
This information relates to downhole well tools and methods for preventing undesired release of well fluids while servicing wells.
2. Description of the Prior Art
U.S. Pat. No. 3,215,203 to P. S. Sizer discloses equipment and methods for inserting and removing a flow conductor from a well. U.S. Pat. No. 3,216,731 discloses well tools and methods for preventing a blowout while moving a flow conductor into and out of a well. Both of these patents are incorporated by reference for all purposes within this application. They both disclose equipment and methods which are used for hydraulic workover of oil and gas wells. This equipment is sometimes referred to as "snubbing" equipment because a flow conductor (work string or wash string of pipe) is inserted into the well against formation fluid pressure rather than overcoming the formation pressure with drilling mud or workover fluids.